Somonauk, IL 60552 Frost Dates
When can you plant in Somonauk, IL?
Typically, the last spring freeze lands around 04/28, roughly 243 days out. The first fall frost typically arrives around 10/13, about 166 frost-free days later.
Somonauk sits in USDA Zone 5b (-15 to -10°F average annual minimum). The dates above are NOAA's 1991-2020 normal at the nearest reporting station, a 30-year average, not a forecast.
What to do before the first frost
About 7 weeks of growing season left in Somonauk before the first fall frost — a cold frame or row cover can stretch harvest weeks past that date.
Why 04/28 isn't a guarantee
04/28 is the middle of 30 years of NOAA records, not a promise. Plant by 04/14 and you're betting against frost in roughly 9 years out of 10. 05/11 is the safer bet, historically only a 1-in-10 chance of frost that late.
How Somonauk compares
At roughly 166 frost-free days, Somonauk places 30,390 of 40,283 ZIP codes in this dataset. Within IL, it ranks 1,481 of 1,548.
Learn more
local microclimates covers what one yard in Somonauk can differ from the 60552 normal. zone vs. frost date covers why Zone 5b and Somonauk's frost date answer different questions.